原文作者：szlcy

原文地址：jdk 1.8 之 ScheduledThreadPoolExecutor 定時任務的退出和取消

package com.dosrain.shunc.trial.schedule;import java.time.LocalDate; import java.time.LocalDateTime; import java.time.format.DateTimeFormatter; import java.util.concurrent.*;public class PoolTest2 {public static void main(String[] args) {// 設置一個同步計算數，目的是讓子線程完成工作后，主線程再繼續工作。// 因為這里只有一個子線程，所以設值為 1CountDownLatch countDownLatch = new CountDownLatch(1);// 創建線程池ScheduledThreadPoolExecutor pool = new ScheduledThreadPoolExecutor(1);// 創建固定時延的定時任務ScheduledFuture<?> scheduledFuture = pool.scheduleWithFixedDelay(new Task2(countDownLatch, 10), 0, 2, TimeUnit.SECONDS);try {// 暫停主線程，等待同步計算數器歸零后，主線程再繼續工作countDownLatch.await();// 同步計數器已歸零，說明定時任務已滿足條件退出// 所以取消定時任務scheduledFuture.cancel(true);} catch (InterruptedException e) {e.printStackTrace();}// 關閉線程池pool.shutdown();} }class Task2 implements Runnable {CountDownLatch countDownLatch;private int counter;public Task2(CountDownLatch countDownLatch, int counter) {this.countDownLatch = countDownLatch;this.counter = counter;}@Overridepublic void run() {LocalDateTime localDateTime = LocalDateTime.now();DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");// 處理一些任務System.out.println(localDateTime.format(dtf) + " [" + Thread.currentThread().getName() + "] " + counter);if (counter-- == 0) {// 判斷達到停止任務的條件countDownLatch.countDown();}} }

程序執行結果：
2020-07-13 15:37:54 [pool-1-thread-1] 10
2020-07-13 15:37:56 [pool-1-thread-1] 9
2020-07-13 15:37:58 [pool-1-thread-1] 8
2020-07-13 15:38:00 [pool-1-thread-1] 7
2020-07-13 15:38:02 [pool-1-thread-1] 6
2020-07-13 15:38:04 [pool-1-thread-1] 5
2020-07-13 15:38:06 [pool-1-thread-1] 4
2020-07-13 15:38:08 [pool-1-thread-1] 3
2020-07-13 15:38:10 [pool-1-thread-1] 2
2020-07-13 15:38:12 [pool-1-thread-1] 1
2020-07-13 15:38:14 [pool-1-thread-1] 0

Process finished with exit code 0

要注意到是2秒打印一次

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